Surface cracks in materials pose reliability concerns in a broad range of industries. For example, in the aircraft industry, a weak point on an aircraft wing flap may begin as a micro-crack which is virtually undetectably by the naked eye. Over time, the micro-crack may grow due to stresses from normal use. In particular, the ends of the crack expand outwardly, and the tip of the crack (i.e., the deep point of the crack) extends even deeper. Eventually, the micro-crack grows into a larger visible crack which is hopefully detected and fixed before a failure results.
One conventional approach to fixing a surface crack in a part (e.g., tiny cracks on aircraft components such as propulsion system plumbing) is to repair the crack by welding. In this approach, welding equipment fuses the two sides of the crack back together. In particular, the welding equipment applies extreme heat to make the area around the crack soft and pasty so that the material along the two sides of the crack melts back together again. In some situations, additional metallic material fuses into or above the crack to provide reinforcement.
Another conventional approach to fixing a surface crack in a part is to drill holes into the part at the ends of the crack. Such drilling rounds out the crack ends thus preventing the crack the growing outwardly any further.
Yet another conventional approach to fixing a surface crack in a part is to simply replace the part. For example, in the context of a wing flap, a team of mechanics simply removes the failed wing flap and installs a new wing flap in its place.